2023-08-13, 09:27 AM
(2023-08-11, 03:49 AM)seandepagnier Wrote: The tighter of a seal you make on a sliding arm the more energy is wasted in friction
I did buy a proper oil seal for it, but it was way too tight. I suspect they're for applications where friction isn't an issue.
Anyway, yesterday I spent a few minutes pouring water onto the ram while moving it in and out, and as I'd hoped I got a little puddle of water in the antechamber but almost nothing in the main chamber. Realistically, if I used it in the pouring rain for hours I'd open it up afterwards and dry it out.
The belt ratio was simply the highest I could achieve with a single belt -- 12t to 80t, or 1:6.66. I couldn't find any reliable specs for the motors I bought on Amazon. One claimed to be 22,000 rpm which I thought was too high, so I bought another which claimed to be 8,000 rpm and as far as I could tell received the same motor. But with the servo.speed.max slider at 50% at I'm getting roughly 100mm per second, and at 100% it's roughly 150mm per second. (That's with it attached to the tiller.) So far it's coped with a bit of weather helm but I haven't tried it in really challenging conditions yet. For the moment this ratio seems to be working. It's worth saying that even after prolonged use on a hot day the motor barely gets warm.
BTW I remember you wondering if a tiller might back-drive a ball screw, but while this does happen to the ball screw in isolation, once it's hooked up to the motor at this sort of ratio I think it'd be impossible.